Monitoring the impact of chlorinated drinking water on the developing gut microbiota of adolescent mice using genetic profiling

Authors: Firrman, Jenni; MULCRONE, PATRICK - Indiana University School Of Medicine; Narrowe, Adrienne; JONES, STEVEN - Children'S Hospital - Philadelphia, Pennsylvania; HU, WEIMING - The Children'S Hospital Of Philadelphia; BITTINGER, KYLE - The Children'S Hospital Of Philadelphia; MOUSTAFA, AHMED - Children'S Hospital - Philadelphia, Pennsylvania; Liu, Lin; XIAO, WEIDONG - Indiana University School Of Medicine

Submitted to: International Journal of Environmental Studies
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/17/2024
Publication Date: 1/16/2025
Citation: Firrman, J., Mulcrone, P., Narrowe, A.B., Jones, S., Hu, W., Bittinger, K., Moustafa, A., Liu, L.S., Xiao, W. 2025. Monitoring the impact of chlorinated drinking water on the developing gut microbiota of adolescent mice using genetic profiling. International Journal of Environmental Studies. https://doi.org/10.1080/00207233.2024.2444847.
DOI: https://doi.org/10.1080/00207233.2024.2444847

Interpretive Summary: In the United States, the practice of water sanitation has been employed for over a century using the chemical chlorine, which inhibits growth of bacteria in water thus limiting the spread of communicable disease. However, not all bacteria are harmful; in particular, within the colon there is a dense community of multiple types of bacteria, referred to as the gut microbiota, that is very important to health and nutrition. This has led us to question whether or not chlorine in drinking water may also impact the gut microbiota and to what extent. To answer this question, male and female mice were bred in a chlorine-free environment and then provided either spring water (no chlorine) or chlorinated water. Feces were collected over the course of 4 weeks in order to compare the gut microbiota between mice. Using DNA sequencing, we found that chlorine had no effect on how many types of bacteria were present and did not cause any major changes to the abundance of these bacteria. However, the results did indicate that the gut microbiota of mice provided chlorinated water had less genes present involved in vitamin B12 synthesis, although the importance of this finding remains unclear as vitamin B12 is consumed as part of a normal diet. In conclusion, the results of this study found that consumption of chlorinated water only had a minimal impact on the gut microbiota.

Technical Abstract: Water chlorination as a method to deter growth of disease-causing microbes has been standard practice in the United States for over a century. Toxicological studies that originally designated chlorinated water as safe for the human host failed to consider the potential impact of chlorine on the gut microbiota, particularly the developing gut microbiota post-weaning. Here, this oversight was addressed through a comparative assessment of the gut microbiota from post-weaned mice (B6) over the course of four weeks provided either chlorine-free water or water containing 1-5 mg/L chlorine. When males and females were considered separately, the only significant impacts of chlorinated water were a decrease in Proteobacteria and Burkholderiaceae at week 2 for females, and Erysipelotrichaceae Ileibacterium at week 3 for males. However, when sex was not considered as a factor and the effects of chlorine over the course of the entire experiment combined, there was a statistically significant decrease in levels of Clostridiaceae 1 and Peptostreptococcaceae. PICRUSt2 analysis found only a minimal impact on antimicrobial resistance genes, but a decrease in several virulence factors associated with porphyrin metabolism which was considered directly related to a significant decrease in 20 genes involved in adenosylcobalamin (Vitamin B12) biosynthesis; A novel finding, although the importance remains unclear. Taken together, the results of this study demonstrated that the gut microbiota of post-weaned mice were resilient to low levels of chlorine and consumption of chlorinated water did not elicit changes to diversity or cause any major community restructuring to occur.